Fluidic carburetor

ABSTRACT

A fluidic carburetor having two fluid pure fluid amplifiers for controlling the rate of fuel flow to the carburetor bore. One fluid amplifier controls fuel flow during cranking and normal running conditions by sensing the vacuum at one point in a Venturi throat and at a second point upstream therefrom, the rate of fuel flow being dependent upon the difference in pressure at the two points. The rate of fuel flow is further controlled by an air temperature sensor and an engine temperature sensor. A second fluid amplifier is provided for feeding additional fuel to the bore during periods of acceleration.

United States Patent Lazar [58] FieldofSearch ..26l/39 A, 39 B,36 A, 69R, 26l/DIG. 69, 39 D; 123/119 R; 137/815 [56] References Cited UNITEDSTATES PATENTS 3,547,414 12/1970 Nardi ..261/DIG. 69 3,574,346 4/1971Sulich ..26l/DIG. 69

AIR TEMP.

[15] 3,655,170 [4 1 Apr.11, 1972 3,548,795 12/1970 Howland ..26l/DlG. 693,556,488 l/l971 Arikawa et al ..26 l/DIG. 69 3,389,894 6/1968 Binder..26l/DlG. 69

Primary Examiner-Tim R. Miles Attorney-Griffin, Branigan and Kindness[57] ABSTRACT A fluidic carburetor having two fluid pure fluidamplifiers for controlling the rate of fuel flow to the carburetor bore.One fluid amplifier controls fuel fiow during cranking and normalrunning conditions by sensing the vacuum at one point in a Venturithroat and at a second point upstream therefrom, the rate of fuel flowbeing dependent upon the difference in pressure at the two points. Therate of fuel flow is further controlled by an air temperature sensor andan engine temperature sensor. A second fluid amplifier is provided forfeeding additional fuel to the bore during periods of acceleration.

6 Claims, 2 Drawing Figures MANIEQLQ VACUUM LOW PRESSURE RETURN PatentedA ril 11, 1972 3,655,170

F I6 I FUEL PREssuR 1 AIR TEMP 0 I I 5e 62 32 34 as f {54 ENGINE TEMP.LOWRIZQIEJSEQSBEJRE MA I Q VAQLJLJM K |'i'| 1 F l G. 2.

LU D Z MA I Q 15;; m C 2 LESS THAN Io HG. O! 'i' 0 COLD ENGINE 3 o dMANIFOLD VACU M I GREATER THAN IdHG. L:1)J U.

AIR FLOW l PER MINUTE INvENToR I BY JEFFREY M. LAZAR ATTORNEYS FLUIDICCARBURETOR OBJECTS OF THE INVENTION The present invention relates to acarburetor including fluid amplifiers for controlling the rate of fuelflow to the carburetor bore.

An object of the invention is to provide a carburetor employing a singlepure fluid amplifier for controlling the rate of fuel flow to thecarburetor bore during cranking, idling, and normal driving conditions.

An object of this invention is to provide a carburetor employing a fluidamplifier having first and second opposing control inputs responsive tothe vacuum sensed at two points in a carburetor bore, said amplifiercontrolling the rate of fuel flow to the carburetor bore duringcranking, idling, and normal driving conditions.

Another object of the invention is to provide a carburetor includingmeans defining a carburetor bore having a Venturi throat therein, afluid amplifier having two opposing control inputs, means for sensingthe vacuum in the throat and upstream therefrom and applying said vacuumto said control inputs, and temperature sensing means for modifying thesensed vacuum applied to one of said control inputs.

A further object of the invention is to provide a carburetor including afluid amplifier, and means controlling the amplifier so that it performsthe function of an accelerating pump.

Still another object of the invention is to provide a carburetorcomprising a pure fluid amplifier, a fluid signal delay means connectedbetween opposing control inputs of the amplifier, and means for applyingmanifold vacuum signals to said control inputs, said manifold vacuumsignals being applied to one of said control inputs through said delaymeans,

whereby the power stream of the amplifier is deflected from one outputto a second for a predetermined interval of time when said manifoldvacuum decreases. Fuel is supplied to the power stream input and isdirected into the carburetor bore through the second output at a ratedependent upon the rate of change of manifold vacuum.

Other objects of the invention and its mode of operation will becomeapparent upon consideration of the following description and theaccompanying drawing.

BRIEF DESCRIPTION OF DRAWING FIG. 1 schematically illustrates apreferred embodiment of the invention; and,

FIG. 2 is a diagram illustrating variations in the fuel to air ratio forvarious operating conditions.

DETAILED DESCRIPTION As shown in FIG. 1, a preferred embodiment of theinvention comprises means defining a carburetor bore CB adapted to passair downwardly therethrough to the intake manifold M of an internalcombustion engine. The carburetor bore has a Venturi section formedtherein and a throttle valve 10 is located downstream from the Venturisection.

The illustrated embodiment of the invention further comprises a fluidiccontrol circuit for supplying fuel to the carburetor bore. The fluidiccontrol circuit includes a first pure fluid amplifier 12, a second purefluid amplifier 14, an engine temperature sensor 16, and an airtemperature sensor 18.

Fluid amplifier 12 comprises a power stream input 20, first and secondcontrol signal inputs 22 and 24, and first and second outputs 26 and 28.The power stream input is connected by way of a fuel supply line 30 tothe high pressure side of a fuel pump (not shown). Output 26 isconnected by way of a fuel line 32 to a noule 33, and output 28 isconnected to a fuel return line 34.

The control input 24 of amplifier 12 is connected to a line 36 whichterminates at an orifice 38 located upstream of the Venturi throat inthe carburetor bore. The control input 22 is connected throughtemperature sensors 16 and 18 to an orifice 40 located in a recess inthe wall of the Venturi throat. The temperature sensors may be capillarytubes having an opening therethrough that tends to restrict fluid flow.

Fluid amplifier 12 is a proportional fluid amplifier of conventionaldesign. Fluid amplifier 12 has an internal configuration such that fuelapplied to power stream input 20 normally flows to output 28 in theabsence of any control signals at control inputs 22 and 24. However, apart or all of the power stream may be directed toward output 26 byapplying a vacuum signal to control input 22 that is greater than avacuum signal applied to control input 24.

Fluid amplifier 12 comprises the primary fuel flow control duringcranking, idling, and normal running conditions and functions in thefollowing manner. Fuel is supplied to the power stream input 20 throughline 30 and the internal configuration of the amplifier causes the powerstream to flow through output 28 to the fuel return line 34. A majorportion of this power stream returns to the fuel supply through line 34.However, because of an adjustable flow restrictor 68, a portion of thepower stream is directed to a control input of amplifier 14 for reasonswhich are subsequently described.

When the engine is cranked, a portion of the power stream of amplifier12 is supplied to the carburetor bore. The throttle valve 10 ispartially opened so that air is drawn downwardly through the carburetorbore by the vacuum created in the intake manifold as the engine iscranked. The air flowing downwardly through the carburetor bore createsa vacuum in the Venturi throat. This vacuum signal is sensed at orifice40 and transmitted through temperature sensors 16 and 18 to controlinput 22 of amplifier 12. The orifice 38 also senses a vacuum signalthat is transmitted over line 36 to control input 24 of the amplifier.Since the vacuum at orifice 40 is much greater than the vacuum atorifice 38, the signal at control input 22 draws the power stream ofamplifier 12 toward output 26 so that a small portion of the fuelcomprising the power stream flows from output 26 through fuel line 32 toorifice 33. At the orifice, the fuel is mixed with the air and movesdownwardly past the throttle valve to the engine manifold.

At the end of the cranking interval, as the engine begins to idle, themanifold vacuum increases thereby drawing air through the carburetorbore at a' faster rate. The negative pressures sensed at orifices 40 and38 are applied to the control inputs of amplifier 12 thereby deflectingmore of the power stream of the amplifier toward output 26. Thissupplies sufficient fuel for idling through output 26 and line 32 tonozzle 33.

Assuming that the engine is cold when started, the point A in FIG. 2represents the fuel to air ratio at curb idle speed. It is well knownthat a warm engine aids in vaporizing fuel. Therefore, when an engine iscold, more fuel must be supplied to the engine than if it were warm, toinsure that sufficient fuel is distributed to each of the cylinders. Forthe same reason, the fuel to air ratio must be varied in accordance withthe temperature of the air flowing into the carburetor bore. Thecapillary sensors 16 and 18 serve the function of controlling the fuelflow so that more fuel is supplied to the carburetor bore when theengine and/or air is cold than when warm, all other operating conditionsbeing constant. Assume that the intake air is at some fixed temperatureand that the engine is cold and idling at curb idle speed. The vacuum inthe Venturi throat draws air into the carburetor bore from orifice 40.This air is drawn from amplifier 12 in the region where power streaminput 20 and control input 22 intersect. It travels through air line 44,capillary 16, air line 46, and capillary 18 to the orifice 40. Whencapillary 16 is cold, it forms a fluid passage that offers littleresistance to fluid flow. Assume for the moment that the same is true ofcapillary 18. Therefore, the vacuum sensed at orifice 40 is manifestedat control input 22 as a vacuum signal of substantially the samemagnitude.

As the engine warms up, the temperature of the engine is sensed bycapillary 16 which may be disposed in the engine cooling system. As thecapillary warms up, it offers increased resistance to the flow of fluidtherethrough. Thus, the vacuum sensed at orifice 40 is manifested atcontrol input 22 as a vacuum signal of smaller magnitude. This smallermagnitude vacuum signal cannot deflect as much of the power stream ofamplifier 12 toward output 26 as the larger magnitude signal could.Therefore, as the engine warms up, less fuel flows through output 26 andline 32 to the nozzle 33. In FIG. 2, the point B represents the fuel toair ratio at curb idle speed once the engine has reached its operatingtemperature.

In view of the foregoing explanation, the operation of the airtemperature capillary sensor 18 is believed obvious. The effect ofcapillary 18 may be visualized by reference to FIG. 2. As the airtemperature of the intake air rises, the line AB shifts to the right.Conversely, as the temperature decreases, the line AB shifts to theleft.

As previously stated, amplifier 12 provides the fuel to the carburetorbore during normal driving conditions. As throttle is opened, more airis drawn through the carburetor bore thereby increasing the vacuum atorifices 40 and 38. However, the vacuum at the Venturi throat increasesat a faster rate than does the vacuum in the region of orifice 38upstream of the throat. Therefore, as throttle 10 is opened the vacuumsignal at control input 22 of amplifier 12 increases in comparison withthe vacuum signal at control input 24. This draws the power stream moretoward output 26 from whence it is injected into the carburetor borethrough nozzle 33.

In FIG. 2, the line AC is a plot of the fuel to air ratio for a coldengine at various running speeds from curb idle (point A) to fullthrottle (point C). The line BD is a plot of the fuel to air ratio for awarm engine at various running speeds from curb idle (point B) to fullthrottle (point D). It will be understood that the line AC approachesand then merges into or becomes the line BD as the engine approaches itsnormal operating temperature.

In a conventional carburetor, a device known as an accelerating pump isprovided for the purpose of supplying additional fuel to the carburetorbore during periods of acceleration. Fluid amplifier l4 performs thefunction of such a pump and comprises a power stream input 50, first andsecond outputs 52 and 54, and four control signal inputs 56, 58, 60 and62.

Power stream input 50 is connected to the fuel supply line 30 so that itreceives fuel at its power stream input whenever the fuel pump isoperating. Output 54 and control input 58 are connected to the fuelreturn line 34. Output 52 is connected to the fuel line 32 whichterminates at orifice 33 in the carburetor bore.

A manifold vacuum sensing means comprising a line 63 terminating at anorifice 64 in the engine intake manifold is directly connected tocontrol inputs 60 and 62 of amplifier 14. The line 63 is furtherconnected through a fluid capacitance or signal delay means 66 to thecontrol input 56.

Fluid amplifier 14 may be a proportional fluid amplifier of conventionaldesign. It has an internal configuration such that in the absence of anysignals at the control inputs, the power stream is normally divided atthe splitter formed at the junction of outputs 52 and 54 so that partflows toward output 52 and part flows toward output 54. However, as willnow be explained, the power stream is controlled so that it only flowstoward output 52 for a short interval of time following an accelerationor opening of throttle valve 10.

During cranking, fuel from supply line 30 is applied to both the powerstream inputs 20 and 50. As previously explained, during cranking amajor portion of the power stream of amplifier l2 flows through output28 to the fuel return line 34. By

proper design of the connecting lines, or by placing a flow restrictor68 in line 34 downstream of its junction with control input 58, aportion of the output from amplifier 12 may be directed to control input58. This deflects the power stream of amplifier 14 toward output 54 fromwhence it flows through line 34 to the return side of the fuel source.

When the engine beings to idle, a smaller portion of the power stream ofamplifier 12 is directed toward output 28 hence the magnitude of thepositive pressure signal at control input 58 is reduced. However, themanifold vacuum increases as the engine begins to idle and this vacuumsignal is applied to control inputs and 62 where it tends to draw thepower stream of the amplifier toward output 54. Thus, the power streamcontinues its flow toward output 54 even though the positive pressuresignal at control input 58 is reduced in magnitude.

Amplifier 14 functions to supply additional fuel to the carburetor boreduring acceleration or when the engine load is increased, the amount offuel supplied being dependent upon the rate of change of manifoldpressure. This is accomplished by differentiating the manifold vacuumsignal by means of fluid capacitance 66, and applying the differentiatedsignal to control input 56 so as to oppose the vacuum signal applied tocontrol inputs 60 and 62.

Consider the case of an acceleration resulting from suddenly openingthrottle valve 10 to its fully opened position. Air flows past thethrottle valve into the manifold thereby suddenly raising the manifoldpressure from the first value (E in FIG. 2) to a less negative value F.The manifold vacuum is sensed at orifice 64 and applied over line 63 tocontrol inputs 60 and 62 of amplifier 14. With less negative pressure atcontrol inputs 60 and 62, the internal configuration of the amplifierdirects more of its power stream toward output 52. From output 52 thepower stream flows through fuel line 32 and is injected into thecarburetor bore through orifice 33.

The less negative manifold vacuum signal is applied to fluid capacitance66 at the same time it is applied to control inputs 60 and 62. Thecapacitance 66 functions in a manner similar to that of an electricalcapacitor in an electrical circuit. Thus, assuming an instantaneouschange from P, to P, at the input of the capacitance, the outputpressure waveform has a sloping front that increases (or decreases) fromP, to P Therefore, at the instant the reduced manifold vacuum signal isapplied to control inputs 60 and 62, the pressure at control input 56 isthe same as before the throttle valve was opened. However, the pressureat control input 56 begins to increase at a rate dependent upon thevolume of capacitance 66. As the pressure at control input 56 increases,the net force resulting from the pressures on opposite sides of thepower stream tends to direct the power stream back toward output 54.When the pressure at control input 56 reaches the value of the manifoldvacuum at control inputs 60 and 62, the power stream of the amplifier isfully deflected so as to flow through output 54 to the fuel return line.

It should be noted that even though the throttle valve may be held inthe fully opened position, the power stream of amplifier 14 is directedtoward output 52 only for the interval of time that it takes thepressure at control input 56 to become equal to the pressure at controlinputs 60 and 62.

On the other hand, if the throttle is controlled so as to raise themanifold pressure at a constant rate at least a portion of the powerstream will be directed toward output 52 as long as the manifoldpressure is increasing. This should be obvious since, if the manifoldpressure is steadily increasing, the pressure at control inputs 60 and62 is always greater than the pressure at control input 56 by a constantamount. The portion of the power stream directed toward output 52 isdetermined by the differential pressures at inputs 56 and inputs 60 and62, and thus is determined by the rate at which the manifold pressureincreases. Of course a limit must be reached where the throttle valvecan be opened no further, at which time the manifold pressure stopsincreasing, and the power stream of amplifier 14 is again directedtoward output 54.

With respect to amplifier 14, it should be noted that fuel underpressure is applied to control input 58 whereas a vacuum signal isapplied to control inputs 60 and 62. This may result in some fuel,either liquid or vapor, being drawn into the manifold through line 63and control inputs 60 and 62. However, the amount of fuel entering themanifold in this manner is less than that required for idling.

Since pneumatic signals are employed to deflect the fuel comprising thepower streams of the amplifiers, there is a mixing of the air and fuel.This promotes vaporization and aids in obtaining a good spray pattern atorifice 33. However, the air should be removed from that portion of thefuel that is recirculated before the fuel is returned to the fuel pump.This may be accomplished by connecting return line 34 to the fuel tank.Alternatively, the return line 34 may be connected through avapor-liquid vessel to the low pressure side of the fuel pump.

While a preferred illustrative embodiment has been shown and described,various modifications in the form and detail thereof may be made withoutdeparting from the spirit and scope of the invention as defined by theappended claims. For example, for purpose of explanation it has beenassumed that the power stream of amplifier would divide equally betweenoutputs 52 and 54 in the absence of any control input signals. By properlimitation of control signals an amplifier may be employed having aninternal configuration such that its power stream is fully or partiallydirected toward output 52 in the absence of any control signals.Furthermore, adjustable flow restrictors such as flow restrictor 68 maybe located in any or all inputs and outputs from the fluid amplifiers toprovide manual adjustment of signal magnitudes.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A fluidic carburetor including means defining a carburetor borethrough which air may flow to the intake manifold of an engine;

a fluid amplifier having a power stream input, first and second outputs,and first, second, third and fourth control inputs;

a fluid capacitance means connected between said first and secondcontrol inputs, said first and second control inputs being disposed onopposing sides of said power stream input;

means for applying a positive pressure signal to said third controlinput that reduces with engine speed, said third control input beingdisposed on the same side of said power stream input as said firstcontrol input;

means for applying fuel to said power stream input;

fuel return means connected to said first output;

means for conveying fuel from said second output to said bore; and,

means connected between said manifold and said second and fourth controlinputs for applying a signal representing manifold vacuum to saidcapacitance means and said second and fourth control inputs,

said control inputs coacting to deflect said power stream to said secondoutput for a predetermined interval of time when said manifold vacuumdrops.

2. A fluidic carburetor as claimed in claim 1 wherein said bore has aVenturi throat formed therein, said carburetor further comprising:

a second fluid amplifier having a power stream input, first and secondoutputs, and first and second control inputs;

first means connected to said first control input and terminating at afirst orifice in said throat for applying a first control signal to saidsecond amplifier dependent upon the vacuum at said throat;

second means connected to said second control input and terminating at asecond orifice in said bore upstream of said throat for applying asecond control signal to said second amplifier dependent upon the vacuumat said second orifice;

means for supplying fuel to the power stream of said second said secondoutput being connected to said fuel return means and to said means forapplying a positive pressure signal to the third control input of saidfluid amplifier; and,

means connected to said second output of said second fluid amplifier forinjecting fuel into said bore,

said first and second control signals controlling said second fluidamplifier to direct more of its power stream to said second output andless to said first output as said first signal increases in magnitudewith respect to said second signal.

3. A fluidic carburetor as claimed in claim 2 and further comprising:

temperature sensing means disposed to sense engine temperature,

said temperature sensing means including means for reducing themagnitude of said first control signal relative to the vacuum at saidthroat as said engine temperature approaches normal operatingtemperature.

4. A fluidic carburetor as claimed in claim 2 and further comprising athrottle valve in said bore downstream of said throat.

5. A fluidic carburetor as claimed in claim 2 wherein said first meanscomprise an air passage including a temperature sensitive capillary tuberesponsive to engine temperature.

6. A fluidic carburetor as claimed in claim 5 wherein said first meansincludes a further temperature sensitive capillary tube disposed in saidbore for sensing the temperature of the air flowing therethrough.

1. A fluidic carburetor including means defining a carburetor bore through which air may flow to the intake manifold of an engine; a fluid amplifier having a power stream input, first and second outputs, and first, second, third and fourth control inputs; a fluid capacitance means connected between said first and second control inputs, said first and second control inputs being disposed on opposing sides of said power stream input; means for applying a positive pressure signal to said third control input that reduces with engine speed, said third control input being disposed on the same side of said power stream input as said first control input; meanS for applying fuel to said power stream input; fuel return means connected to said first output; means for conveying fuel from said second output to said bore; and, means connected between said manifold and said second and fourth control inputs for applying a signal representing manifold vacuum to said capacitance means and said second and fourth control inputs, said control inputs coacting to deflect said power stream to said second output for a predetermined interval of time when said manifold vacuum drops.
 2. A fluidic carburetor as claimed in claim 1 wherein said bore has a Venturi throat formed therein, said carburetor further comprising: a second fluid amplifier having a power stream input, first and second outputs, and first and second control inputs; first means connected to said first control input and terminating at a first orifice in said throat for applying a first control signal to said second amplifier dependent upon the vacuum at said throat; second means connected to said second control input and terminating at a second orifice in said bore upstream of said throat for applying a second control signal to said second amplifier dependent upon the vacuum at said second orifice; means for supplying fuel to the power stream of said second amplifier; said second output being connected to said fuel return means and to said means for applying a positive pressure signal to the third control input of said fluid amplifier; and, means connected to said second output of said second fluid amplifier for injecting fuel into said bore, said first and second control signals controlling said second fluid amplifier to direct more of its power stream to said second output and less to said first output as said first signal increases in magnitude with respect to said second signal.
 3. A fluidic carburetor as claimed in claim 2 and further comprising: temperature sensing means disposed to sense engine temperature, said temperature sensing means including means for reducing the magnitude of said first control signal relative to the vacuum at said throat as said engine temperature approaches normal operating temperature.
 4. A fluidic carburetor as claimed in claim 2 and further comprising a throttle valve in said bore downstream of said throat.
 5. A fluidic carburetor as claimed in claim 2 wherein said first means comprise an air passage including a temperature sensitive capillary tube responsive to engine temperature.
 6. A fluidic carburetor as claimed in claim 5 wherein said first means includes a further temperature sensitive capillary tube disposed in said bore for sensing the temperature of the air flowing therethrough. 